Roughly 10% of the population primarily use their left hand. This happens because the brain is divided into two hemispheres. The right side of the brain controls movement on the left side of the body and vice versa.

But why humans develop "handedness," or a preference for one side over the other, is still somewhat a mystery.

Because left-handedness tends to run in families, scientists believed for years that handedness was linked to a gene, but could not identify the exact one, according to The New York Times.

A 2013 study published in PLOS Genetics found that a network of genes may determine a person's handedness, as opposed to just one. "In reality, the research suggests that handedness could be more subtle than simple 'dominant' or 'recessive' traits – a whole host of genes might play significant roles," Natasha Geiling wrote about the study on Smithsonian.com.

Photos of famous lefties:

Oprah Winfrey waves her left hand at the premiere of The Weinstein Company's "Lee Daniels' The Butler" at Regal Cinemas L.A. Live in 2013. (Photo: Jason Merritt, Getty Images)

Catherine, Duchess of Cambridge, and Prince William, Duke of Cambridge, gesturing with his dominant left hand, mark the 100th anniversary of Great Britain declaring war on Germany on Aug. 4 in Mons, Belgium. (Photo: Samir Hussein, WireImage)

President Obama signs a resolution which provides for $225 million in supplemental emergency funding to Israel for the Iron Dome missile defense system in the Oval Office on Aug. 4. (Photo: Saul Loeb, AFP/Getty Images)

Annie Lennox of Eurythmics performs onstage during "The Night That Changed America: A GRAMMY Salute to The Beatles" at the Los Angeles Convention Center on Jan. 27. (Photo: Kevin Winter, Getty Images, for NARAS)

Phil Mickelson hits out of the fairway on the 15th hole during the final round of the 2014 PGA Championship golf tournament at Valhalla Golf Club in Louisville on Aug. 10. (Photo: Brian Spurlock, USA TODAY Sports)

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1. Three of the last four presidents have been left-handed: President Obama, President George H.W. Bush and President Clinton.

2. The percentage of left-handed people (about 10% of the population) to right-handed people has stayed consistent over time. That includes studies of handprints on ancient cave paintings and analysis of ancient artifacts, according to The New York Times.

3. LOOGY in baseball stands for "left-handed, one-out guy." It's a term for a relief pitcher who throws left-handed and specializes in pitching to left-handed batters.